The enzyme catalase (EC The enzyme catalase from both animal and plant sources is light sensitive (2,4,7,23 we investigated the dynamics of the catalase polypeptide with labeling and chase experiments and immunochemical techniques; for comparison, we investigated the dynamics of the Dl protein in rye leaves exposed to different photon flux densities.The maintenance of proteins depending on rapid tumover will generally be sensitive to all environmental conditions that either overload or hamper the capacity of repair synthesis, as previously described for low temperature (29). Also, other stress conditions known to affect protein synthesis, such as salt (13, 16) or heat shock (28), can be expected to induce specific declines in catalase and possibly in the Dl protein even in only moderate light, simply by preventing repair. Therefore, their influence on catalase and on Dl was investigated.
MATERIALS AND METHODS
Plant Material and Growing ConditionsExperiments were performed with leaf sections of 6-d-old rye seedlings (Secale cereale L. cv Halo). Seeds were surface sterilized by a 10-min vacuum infiltration and about 30-min soaking in a freshly prepared, filtered solution of 3% (w/v) calcium hypochlorite chloride, thoroughly washed with demineralized H20, and grown at 220C in glass-covered plastic boxes on filter paper (Schleicher & Schull; No. 598